i bought this new aqua-green CT female at petco yesterday in a moment of weakness. she had stripes when i brought her home but because it was a new shipment i thought it was just cause of all the movement. but when i got her home during water changes she sat next to Spark my blue delta male and her stripes went away. i tested this by separating them with paper then when i see stripes i take it away with in 3 min her stripes are gone.

any suggestions i have spark in isolation for breeding with both this female or my other female Dart

I'm not sure what you are actually asking. But some individuals will mostly show their stress color if alone. Only when they see other bettas, their mentality kicks in and change into vibrant colors. This is normal.

These colors are called "stress stripes/lines" because that's what ALL bettas show when stressed. But actually this color is not always associated with stress. A relaxed betta with nothing to fear no need to protect itself sometimes show this color too.